U.S. patent application number 11/986263 was filed with the patent office on 2008-05-22 for liquid film applicator assembly and rectilinear shearing system incorporating the same.
Invention is credited to Yuri A. Bobrov, David Harwood McMurtry, Mikhail Vitoldovich Paukshto.
Application Number | 20080115724 11/986263 |
Document ID | / |
Family ID | 39430366 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080115724 |
Kind Code |
A1 |
McMurtry; David Harwood ; et
al. |
May 22, 2008 |
Liquid film applicator assembly and rectilinear shearing system
incorporating the same
Abstract
A liquid coating applicator with a very precise means for
controlling gap thickness as well as adapting to non-planar
discontinuities in the substrate.
Inventors: |
McMurtry; David Harwood;
(Felton, CA) ; Paukshto; Mikhail Vitoldovich;
(Foster City, CA) ; Bobrov; Yuri A.; (Menlo Park,
CA) |
Correspondence
Address: |
Owen J. Bates
1143 Beaconsfield Road
San Jose
CA
95121
US
|
Family ID: |
39430366 |
Appl. No.: |
11/986263 |
Filed: |
November 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60860230 |
Nov 21, 2006 |
|
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|
Current U.S.
Class: |
118/300 |
Current CPC
Class: |
B05C 11/028 20130101;
G02B 5/3083 20130101; G02B 5/3016 20130101 |
Class at
Publication: |
118/300 |
International
Class: |
B05B 7/00 20060101
B05B007/00 |
Claims
1. A liquid coating applicator comprising: a. a left and a right
longitudinal side member each having the form of a wedge-like rail;
each side member having an upper surface and a base surface with
said base surfaces of the two side members forming a base plane and
the upper surface of said left side member forming an angle alpha-L
with respect to said base surface of said left side member and the
upper surface of said right side member forming an angle alpha-R
with respect to said base surface of said right side member; b. a
bridge having a planar shear surface, a front surface, a rear
surface, a rear edge, and a transition surface; said bridge having
a left and a right bridge wedge surfaces; said left bridge wedge
surface forming an angle alpha-L with respect to said planar shear
surface and said right bridge wedge surface forming an angle
alpha-R with respect to said planar shear surface; c. a clamp
member adapted to adjustably and fixedly secure the bridge and each
of said side members such that said bridge is positioned between
the two side members such that base surface of each of said rails
and the planar shear surface of the bridge are approximately
co-planar and the distance d from the base plane to the mid-point
of the planar shear surface being greater than or equal to about 0
microns; each of said upper surfaces of said left and right side
members being in contact with one of said left and right bridge
wedge surfaces respectively and wherein distance d can be altered
by repositioning said side members with respect to said bridge
prior to securing said side members and said bridge within said
clamp; wherein when a coating liquid is disposed upon a substrate
and said liquid coating applicator and the substrate are translated
relative to each other such that the substrate moves toward said
front surface of said bridge a liquid coating is formed on the
substrate.
2. The liquid coating applicator according to claim 1, wherein said
transition surface is a curved surface connecting said front face
of the bridge and said planar shear surface of said bridge.
3. The liquid coating applicator according to claim 2, wherein said
transition surface has a radius of at least 50 microns.
4. The liquid coating applicator according to claim 1, wherein said
bridge comprises an upper bridge member and a lower bridge member
having mating surfaces wherein the mating surfaces form an angle
gamma degrees with respect to the planar shear surface.
5. The liquid coating applicator according to claim 4 wherein said
angle gamma is less than or equal to angle alpha-L or alpha-R.
6. The liquid coating applicator according to claim 1 wherein said
planar shear surface forms an angle of less than 2 degrees with
said base plane.
7. The liquid coating applicator according to claim 6 wherein said
planar shear surface forms an angle of less than 10-arc minutes
with said base plane.
8. The liquid coating applicator according to claim 7 wherein said
planar shear surface is parallel to said base plane.
9. The liquid coating applicator according to claim 1 wherein said
angle alpha-L equals alpha-R.
10. The liquid coating applicator according to claim 1 wherein said
distance d can be adjusted to be in the range of about 0 to about
100 microns.
11. The liquid coating applicator according to claim 1 wherein said
rear face makes an angle with said planar shear surface of at least
about 90 degrees.
12. The liquid coating applicator according to claim 1 wherein said
rear face makes an angle with said planar shear surface in the
range of about 90 degrees to about 135 degrees.
13. The liquid coating applicator according to claim 1 wherein the
length of said shear zone is in the range of about 0.25 inches to
about 2 inches.
14. The liquid coating applicator according to claim 1 wherein the
length of said shear zone is greater than d.
15. The liquid coating applicator according to claim 1 wherein said
longitudinal side members are parallel.
16. The liquid coating applicator according to claim 1 further
comprising an offset in the lower surface of each of said
longitudinal side members, said offsets having a horizontal and
vertical dimension which are optimized to minimize capillary creep
of a coating liquid.
17. The liquid coating applicator according to claim 1 further
comprising an offset in left and right lower surface of said
bridge, said offsets having a horizontal and vertical dimension
which are optimized to minimize capillary creep of a coating
liquid.
18. A coating device comprising: a. a compliant assembly comprising
a fixed member having an anchor attachment clamp, and adapted to
securely receive one or more flex strips; a compliant member having
an inner surface, an outer surface and a lower surface, said
compliant member adapted to securely receive a liquid film
applicator and one or more flex strips; each of said fixed member
and compliant member having an inner and an outer face; the two
inner faces facing towards each other and each outer face oriented
away from each other; and one or more flex strips securely mounted
between said fixed member and said compliant member wherein said
compliant member is free to translate in the positive and negative
Tz direction and rotate in both a positive and negative direction
about the Rx axis and the Ry axis; and b. a liquid coating
applicator as described in claim 1; said outer face of said
compliant member is attached to one side of said clamp and said
lower face of said compliant member is higher than said base plane;
and wherein when said coating device is moved relative to a
substrate the liquid coating applicator is compliant with changes
in the surface of the substrate.
19. A coating device as described in claim 18 wherein said outer
face of said compliant member is attached to one side of said clamp
such that the front face of said bridge is directly facing said
outer face of said compliant member.
20. A coating device as described in claim 18 wherein said outer
face of said compliant member is attached to one side of said clamp
such that the rear face of said bridge is directly facing said
outer face of said compliant member.
Description
RELATED APPLICATIONS
[0001] This application claims benefit of the provisional
application 60/860,230 filed on 21 Nov. 2006.
FIELD OF THE INVENTION
[0002] The present invention refers to the field of formation of
thin-film coatings using flowable substances. More specifically,
the invention refers to facilities for obtaining thin films or
coatings possessing anisotropic physical properties.
BACKGROUND OF THE INVENTION
[0003] Various types of wet film applicators, in particular, those
used for testing paints, are known from the prior art. For the
correct determination of some special properties of coatings such
as color, transparency, luster, strength, resistance to weathering
and chemical factors, etc., it is necessary to ensure that the test
coatings applied in sequential runs would have the same preset
thickness. In addition, it is desired that the applicator device
would be adjustable so as to obtain the films of the desired
thickness from various substances having varied physical
properties.
[0004] One wet film applicator known from the prior art comprises a
pair of wedge-shaped elements, which are parallel to each other and
bear a transverse plane blade forming the coating. A gap between
the bottom edge of the blade and the base plane (substrate)
determines the thickness of the applied coating. The thickness of
this gap is varied when the blade is moved along the wedge-shaped
elements. Once the required gap thickness is set, the mutual
arrangement of parts in the device is fixed. The blade is oriented
perpendicularly to the direction of application and forms a film of
desired thickness when the applicator is moved relative to the
substrate surface. This device is quite universal and provides the
level of accuracy that is sufficient for the formation of usual
paint, lacquer, and other wet film coatings. In the clamping
mechanism, the tightening screws directly presses against the blade
which imparts a twisting motion to the blade However, neither this
accuracy of this device nor (which is more important) the mode of
device interaction with the applied liquid are sufficient for the
formation of high-quality optically anisotropic films and coatings,
especially such as are employed in modern multilayer interference
devices.
[0005] Thin films with anisotropic optical properties, which are
formed using liquid-crystalline solutions of organic dyes, are now
widely used in science and technology. The molecules of these
organic compounds have planar configuration and form
orientation-ordered supramolecular complexes in solution. When a
solution of these organic molecules is applied onto a substrate
surface in the presence of an external orienting action
(alignment), the resulting coating acquires a macroscopic
orientation (optical anisotropy), which is not only retained in the
course of subsequent drying but can even increase as a result of
crystallization. The polarization axis is oriented along the
direction of the aligning action, which coincides with the
direction of application of the coating. Specific structural
features of such optical films determine the need for developing
special coating devices capable of forming precise thin layers with
the required molecular orientation.
[0006] There are various known methods for the formation of
optically anisotropic films and, accordingly, various devices which
implement these methods. For example, liquid-crystalline solutions
can be applied using a drawing plate or a wiper (squeegee), which
can be of a blade (sheet) or cylinder type. The application of a
liquid-crystalline solution onto a substrate surface can be
performed simultaneously with the orientation of supramolecular
complexes in a required direction. However, devices known in the
prior art do not ensure the formation of highly anisotropic films
with reproducible characteristics, which is explained by
unavoidable disruption of the oriented molecular structure (defect
production) during the film formation. In addition, the technology
of film formation using the known devices requires prolonged
preliminary work for determining the optimum application conditions
for every batch of the initial raw materials.
[0007] Attempts at solving the aforementioned problems led to the
creation of rather complicated devices, in particular, those
containing liquid feed channels of special shapes, additional
smoothing elements, etc.
[0008] Applicators known in the prior art also include devices of
the slot-die coating system type such as the Sony setup (Alabama,
USA), Cambridge Shearing System (Linkam Scientific, UK), sliding
plate rheometers (FMR-MIT, USA), etc.
[0009] Patents depicting various devices of the prior art are U.S.
Pat. No. 4,299,789, November 1981, Giesbrecht;
[0010] U.S. Pat. No. 4,869,200, September 1989, Euverard; U.S. Pat.
No. 6,174,394, 16/2001, Gvon et al.; WO 02/087782, July 2002,
Lazarev et al.; and WO 02/056066, July 2002, Lazarev et al.
[0011] Despite the existing solutions, problems are still
encountered that are related to the need for combining the
necessary properties in one device, including high accuracy, simple
adjustment, control over the film parameters (in particular,
thickness), and the possibility to improve the quality of applied
coatings by compensating for substrate unevenness.
[0012] The uniqueness of the device according to the present
invention is the ability to obtain coatings of large areas at a
high rate of application, low consumption of the raw material, and
high-precision control over the film thickness and optical
parameters (Mueller matrix, alignment, etc.). Additional important
advantage of the proposed device is a sufficiently large size of
the zone of shear action.
SUMMARY OF THE INVENTION
[0013] The present invention refers to devices intended for
controlled coating substrate surfaces with liquid (flowable)
substances and forming the desired material structure due to the
shear between two planes sliding relative to each other. The aim of
this invention is to obtain films with improved physical
characteristics and increased reproducibility of results, not only
over the area of single coating, but within a series of films
formed from a single stock solution of coating liquid as well as
from one batch to another.
[0014] A liquid coating device according to the present invention
comprises
[0015] (i) an applicator assembly, and a
[0016] (ii) a compliant assembly for holding the applicator and
compensating for unevenness in the surface of the substrate.
[0017] Though the combination of the two components above produces
the best thin film coatings, it is possible to produce a thin film
coatings with just the applicator assembly as discussed below
[0018] The above system is typically used in conjunction with an
essentially planar substrate, and a substrate holder with a means
of linear transportation of the compliant assembly/liquid film
applicator relative to the substrate holder. For purpose of
identifying various degrees of freedom, FIG. 2 identifies the
proper orientation of the three axis Tx, Ty, and Tz with respect to
the coating device and the three rotations about these axis: Rx,
Ry, and Rz. The arrows indicate translation or rotation in the
positive direction. The compliant assembly permits motion of the
liquid film applicator in only three degrees of freedom, which are
translation in the plus and minus Tz direction and rotation in the
plus and minus directions: Rx and Ry.
[0019] The liquid film assembly is designed to be in direct
physical contact with the substrate by way of the two parallel
rails mounted on opposite sides of the bridge. A sample of the
liquid to be coated is placed on the substrate along the front edge
of the bridge. As the coating assembly is translated relative to
the substrate, the coating liquid is drawn into the gap formed by
the lower planar surface of the bridge and the substrate. Because
of the compliant nature of the compliant assembly, the liquid film
applicator will ride on the surface of the substrate and follow the
minute variations in the surface of the substrate, limited by the
three degrees of freedom discussed above.
[0020] This method makes possible the compensation of the linear
and angular displacements arising during the system operation and
ensures high homogeneity and smoothness of the applied film even on
a rough (wavy) substrate. In the case of thin optical films,
deviations of the substrate surface from the horizontal plane
(waviness) can be comparable with the film thickness, which
frequently leads to distortions and detrimentally influences the
optical device performance. Retention of specific degrees of
freedom described above in the Compliant Assembly 110 design allows
the Applicator Assembly 120 to follow the substrate surface, thus
increasing the uniformity of coating.
[0021] A liquid film applicator according to the present invention
comprises [0022] (i) at least two longitudinal wedge-like rails
with their bases occurring in the same plane called the base plane;
[0023] (ii) a bridge which spans the two side members, which has at
least one flat face and is in contact with each rail in at least
one point; and [0024] (iii) a clamp system ensuring strict fixation
of the bridge at any preset position in relation to the rails, such
that a gap thickness of the desired dimension can be obtained
[0025] The bridge can be moved along both rails so that the flat
face of the bridge makes a certain constant dihedral angle within
0-10 arc minutes with the base plane, and the gap between this face
and the base plane has a thickness from about 0 to about 100
microns. The bridge makes contact with each rail along the upper
surface of the rail. The front flat face of the bridge makes a
smooth continuous curved transition to the lower planar shear face
with said transition typically being a one quarter circular arc
having a radius of R.
[0026] The coating device according to the disclosed invention is a
universal setup, which ensures excellent results at a relative
simplicity of adjustment and high convenience in use. The disclosed
coating device is capable of forming high precision coatings [0027]
at shearing speeds of up to 1000 mm/sec; [0028] with very low
coating liquid material consumption (less than 1 cc) [0029]
Precisely controlled gap thickness (in the range 0-100 microns) and
[0030] Long length of shearing zone (up to 30 mm)
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Having just described the invention in general terms, other
and further objects, features, and advantages of the invention will
be made more explicit from the following detailed description taken
with reference to the drawings, which are not necessarily drawn to
scale, and wherein:
[0032] FIG. 1 is a perspective view of one embodiment the Coating
Device of the present invention;
[0033] FIG. 2 is a perspective view of one embodiment of the
Compliant Assembly;
[0034] FIG. 3 is a perspective view of one embodiment of the
Applicator Assembly;
[0035] FIG. 4 is a sectional view of one embodiment of the
Applicator Assembly;
[0036] FIG. 5A is side view of the bridge, the substrate and a
sample of the liquid coating;
[0037] FIG. 5B is side view of the bridge showing the showing a
Read Edge with a different theta angle;
[0038] FIG. 5C is a side and end view of the bridge and rails
showing the gap d and wedge angle a;
[0039] FIG. 6 is a wire frame model of showing a line of contact
between the rails, the bridge and the substrate;
[0040] FIG. 7 is a sectional view of an alternative embodiment of
the bridge; and
[0041] FIG. 8 is a sectional view of various configurations of the
contact surfaces between the bridge the upper surfaces of the
rails.
DETAILED DESCRIPTION OF THE INVENTION
[0042] Referring now primarily to FIG. 1 a Coating Device 100
according to the disclosed invention comprises an Applicator
Assembly 120 (FIG. 3), and a Compliant Assembly 110.
[0043] The Applicator Assembly 120 is securely attached to one end
of the Compliant Assembly 110 and the other end of Compliant
Assembly is secured to fixed a mechanical anchor (not shown) via
Clamp 160 (FIG. 2). Further details of both the Complaint Assembly
and the Applicator Assembly will be discussed below.
[0044] The Coating Solution that is to be formed into a thin film
is placed on the Substrate 105 just in front of Bridge 210. Then
Substrate 105 is moved from left to right, causing Coating Solution
108 to be dragged under Applicator Assembly 120 causing Thin Film
Coating 109 to be formed.
[0045] All references to motion and direction of motion of the
substrate are to be understood to be relative to the coating
device. It is possible to have the coating assembly fixed to an
anchor and the substrate move. Alternatively it is possible to have
the substrate fixed and move the coating assembly by attaching a
mechanical means of motion to the coating device, preferably by way
of the Clamp 160. A third possibility would be have both the
substrate and the coating device actually moving. All three
possibilities will be understood to be encompassed within
references to motion of the substrate of the Coating Device
100.
[0046] Compliant Assembly 110, shown in both FIGS. 1 and 2, is
attached to the Applicator 120. Compliant Assembly 110 provides a
means to position the Applicator 120 relative to the Substrate 105.
The transportation is usually performed using a worm mechanism with
a step motor. However, embodiments of the present invention are not
restricted to mechanisms of this type. Any means that ensures the
smooth transport of the Coating Device 100 relative to Substrate
105, with the required velocity can be employed. The optimum
relative velocity has to be selected taking into account the
Theological properties of particular coating liquid.
[0047] The second important assembly of Coating Device 100 is the
Applicator 120 (shown as part of the overall Coating Device 100 in
FIG. 1 and by itself in FIGS. 3 and 4), which includes
[0048] (i) at least two longitudinal Rails 220A and 220B. The lower
portion of the Rails 220A/B make contact with the Substrate 105
along Contact Surfaces 225A and 225B. The Contact Surfaces 225A and
225B are narrower than the overall width of Rail 220A and 220B and
thus form Rail Offsets 230A and 230B the upper surfaces of which
are at a distance D1 (FIG. 4) from the Contact Surfaces 225A and
225B. The Rail Offsets also have a horizontal dimension D2 (FIG.
4). The distances D1 and D2 are preferably 0.02 to 0.5 inches.
[0049] The Rail Offsets 230A and 230B hinder the migration of
Coating Liquid 108 which leaks from each edge of the Planar Shear
Surface 250 facing each of the Rails 220A and 220B so that the
Coating Liquid 108 tends to cling to these edges by capillary
action and does not reach the interfaces between Contact Surfaces
225A and 225B and Substrate 105. If any Coating Liquid did get
underneath the Contact Surfaces, the ability of the Applicator 120
to properly follow the surface of Substrate 105 would be
compromised and thus the quality of the Coating 109 formed.
[0050] In the alternative, it is possible to have an equivalent
offsets formed within each side of Bridge 210. Offsets located
within the Bridge would function in exactly the same manner as the
offsets shown in FIG. 4.
[0051] Located along the upper portion of each Rail are Rail Wedge
Surfaces 235A and 235B respectively. This surface is angled with
respect to the Contact Surfaces 225A and 225B. This angle is
referred to as "a" and is preferably in the range of 1 minute to 60
minutes.
[0052] (ii) Clamp 200 is designed for two primary functions. The
first is to securely hold Bridge 210 and Rails 220A and 220B.
Bridge 210 is mounted between the Rails 220A and 220B. Rails 220A
and 22B make contact with Clamp Contact Surfaces 285A and 285B.
Bridge 210 is positioned between the two Rails. All clearances are
such that the Rails and the Bridge form a snug, but adjustable fit
within Clamp 200. Once the Rails and Bridge are properly positioned
(discussed below) they are securely tightened within Clamp 200.
This is accomplished by tightening Clamp Screws 260 in Threaded
Hole 263 which then pushes against Clamp Flex Member 280. Clamp
Slit 270 weakens the structure just enough to allow Clamp Flex
member 280 to be biased against the Rails and the Bridge, thus
holding them securely in place.
[0053] (iii) Bridge 210 is T-shaped structure that contacts the
Rails along the inner parallel face of each of the Rails as well as
along the upper Rail Wedge Surfaces 235A and 235B. Bridge 210 has
two Bridge Wedge Surfaces 240A and 240B which are the surfaces
which contact the Rail Wedge Surfaces 235A and 235B. The Bridge
Wedge Surfaces 240A and 240B have the same slope as the Rail Wedge
Surfaces 235A/235B. Thus when the two Rails are moved relative to
the Bridge, they are urged in a vertical direction with respect to
the lower flat surface of the bridge, Planar Shear Surface 250.
Typically the Rails are adjusted so that they extend slightly
beyond Planar Shear Surface 250. When the Applicator Assembly is
placed on Substrate 105, this difference causes Gap 237 (FIG. 4,
FIG. 5A and FIG. 5C) to be formed between Planar Shear Surface 250
and Substrate 105. Gap 237 has a thickness d when measured from the
mid-point of the Planar Shear Surface to the Substrate 105.
[0054] It should be noted that it is critical that each mating pair
of Bridge Wedge Surfaces 240A/Rail Wedge Surface 235A and Bridge
Wedge Surfaces 240B/Rail Wedge Surface 235B have the same angle,
but it is not critical that each pair has the same angle as the
other pair.
[0055] Because the whole Applicator Assembly rides the substrate on
the two Rails, the Planar Shear Surface 250 will be positioned
above the surface of the Substrate 105. This gaps controls the
thickness of the Coating 109.
[0056] The width of the bridge 212 (FIG. 4) is determined by the
required width of the coating, while the length of the Shear Zone
217 (FIG. 5) is based in part upon the Theological properties of
the coating liquid and relative velocity between Substrate 105 and
Planar Shear Surface 250. The extended length of Shear Zone 217 is
a significant feature and provides an important means of adapting
the Applicator Assembly to Coating Liquids 108 having a wide
variety of properties.
[0057] The Front Face 247 of the bridge makes a smooth continuous
curved Transition Surface 245 to the Planar Shear Surface 250 with
a curvature radius R of sufficient size to uniformly pull the
Coating Liquid 108 into the gap and cause its homogeneous spreading
under the Planar Shear Surface 250. The size of the radius R is
dependant in part on the rheological properties of the Coating
Liquid 108 and the relative velocity between the Planar Shear
Surface 250 and the Substrate 105 and is typically greater than 50
microns. Though the smooth curved transition is shown in this
embodiment as a 1/4 radius circle, there is no requirement that the
curved transition be circular, and other shapes and curvatures may
be employed as the characteristics of the liquid solution
dictate.
[0058] The Shear Zone 217 extends from point where the Transition
Surface 245 meets the Planar Shear Surface 250 and the Rear Edge
255.
[0059] The Planar Shear Surface 250 intersects with the smooth Rear
Surface 248 at a sharp angle theta (See FIGS. 5A and 5B) forming
sharp Rear Edge 255A. (FIG. 5A) of about 90 degrees or greater
(e.g. Rear Edge 255B, FIG. 5B) such that a sharp Rear Edge 255,
which is devoid of irregularities, exists between said Planar Shear
Surface 250 and said smooth Rear Surface 248 so as to avoid
end-sticking of the wet layer to Rear Surface 248
[0060] The plane of the Planar Shear Surface 250 is usually
parallel to the base plane. However, depending on the rheological
properties of the coating liquid and the required parameters of
coating, the Planar Shear Surface 250 can make an angle .beta.
(FIG. 7) that is typically within 10-30 arc minutes with the base
plane (the front edge can be either higher or lower than the rear
edge). By varying this angle, it is possible to control the shear
stress on the Coating Liquid 108 lying with the gap and change the
mode of application and release of this stress. The angle between
the Planar Shear Surface 250 and the base plane is usually changed
by replacing the whole Bridge 210.
[0061] The Planar Shear Surface 250 must be a smooth and have a
mirror-like surface and flat to within 1-3 wavelengths over the
entire surface (0.3-1 micron)
[0062] Gap 237 between the Planar Shear Surface 250 and the
Substrate 105 has a thickness d which is typically within the range
of about 0 microns to about 100 microns. Thickness d of Gap 237 can
be changed by precisely shifting the Rails with respect to the
Bridge 210. Because the Rails are longer than the depth of the
Clamp and Bridge, the Rails can be positioned anywhere along their
length. However, the Bridge 210 is typically centered, front to
back within the Clamp 200. The wedge angle a, must provide for the
smooth control and precise setting of the gap thickness and with
the required accuracy (typically, about 20 nm). When it is
necessary to change the parameters and/or thickness of the applied
coating, the Applicator 120 is removed from the Coating Device 100
and placed upside down with the Contact Surfaces 225A/225B and the
Planar Shear Surface 250 facing upwards.
[0063] Initially the rails are adjusted so that the Contact
Surfaces 225A/225B and Planar Shear Surface 250 are all coplanar.
Then because, the wedge angle a is known, the Rails 220A/220B can
be moved a precise distance relative to the bridge, which
translates into the desired change in the distance between the
plane formed by the Contact Surfaces 225A/225B and Planar Surface
250.
[0064] The actual gap distance can be measured and confirmed by
measuring an interference pattern that arises due to multiple
reflection of a light beam between the Planar Shear Surface 250 and
a glass plate used for the testing which rests upon the Contact
Surfaces 225A/225B
[0065] In one possible alternative embodiment (FIG. 7), the Bridge
210 is made up of two wedge-like elements (215 and 216), which
allow for a relative shift along the slippage plane, which is
inclined relative to the base plane at an angle .gamma., which is
smaller than angle a. This alternative design of the Bridge 210
member is convenient for the additional fine adjustment of the gap
thickness d.
[0066] In second alternative embodiment of the Bridge 210, some or
all of the material forming Bridge 210 can be a essentially
transparent.
[0067] Although most depictions of the Bridge 210 shown herein have
the bridge made of a single monolithic member, it is within the
scope of the invention that the Bridge 210 could be made of two or
more elements as long as the assembly of these components provides
the same functionality as a monolithic bridge.
[0068] The site of the contact between the Bridge Wedge Surfaces
and the Rail Wedge Surfaces must, on the one hand, ensure a
reliable and strong structure of the Applicator Assembly 120 and,
on the other hand, provide for their free and high-precision mutual
displacement. FIG. 8 shows a cross section of four alternative
embodiments of the contact sites, which can provide for the
required quality and properties of these contact surfaces. However,
the possible embodiments are not restricted to these variants and
admit any other structures which provide the needed physical
requirements.
[0069] The liquid film applicator according to the present
invention usually employs two identical wedge-like rails. However,
embodiments incorporating other configurations of wedge-like rails
are possible as well.
[0070] A schematic depiction of the minimum requirement for the
Bridge and Rail contact surfaces is shown in FIG. 6. The minimum
required contacts between Bridge 210A and Rail 221A and 221B is
shown as line TW1 and TW2. Likewise the minimum required contact
between Rail 221A and 221B and Substrate 105 are depicted as lines
TS1 and TS2. All references to contact surfaces and contact between
contact surfaces contained herein shall be understood to include at
least one line of contact between the surfaces. Though the contact
surfaces as shown in the various embodiment contained herein are
shown as flat surfaces, such contact surfaces may include any
number of configurations as long as there is a single line of
contact between the surfaces.
[0071] Though the best films can be performed when the Compliant
Assembly 110 "drags" the Applicator Assembly 120 across the
substrate, it is possible to attach the Complaint Assembly 110 to
Clamp 200 by rotating Compliant Assembly 180.degree. around the Tz
axis (from its position shown in FIG. 1 where Compliant Member 140
is attached to Inner Face 147) and attaching Compliant Member 140
to Outer Face 145 (FIG. 3) of Clamp 200. Then Compliant Assembly
110 can "push" Applicator Assembly 120. This configuration still
allows the Complaint Assembly to control/limit the movement of the
Applicator Assembly 120 to the three degrees of freedom previously
discussed. It should be noted that the stress on the system in this
configuration must be kept below the buckling limit of Flex Members
150.
Applications:
[0072] Preferred coating liquids for the formation of anisotropic
optical films include liquid colloidal systems containing
anisometric particles, in particular, lyotropic liquid crystals of
organic dyes. Examples are offered by organic dyes such as
indanthrone (Vat Blue 4), 1,4,5,8-naphthalenetetracarboxylic acid
dibenzimidazole (Vat Red 14), 3,4,9,10-perylenetetracarboxylic acid
dibenzimidazole, and quinacridone (Pigment Violet 19), and some
other whose derivatives or their mixtures are capable of forming
stable lyotropic liquid crystal phases.
[0073] When such an organic compound is dissolved in an appropriate
solvent, a colloidal system (liquid-crystalline solution) is
formed, in which organic molecules combine to form c representing
kinetic units of the colloidal system. A liquid-crystalline liquid
is a preferred coating liquid, from which a desired anisotropic
crystalline film (also called thin-film crystal) is formed in the
course of application, orientation of the liquid-crystalline
solution, and subsequent removal of the solvent.
[0074] This colloidal system must possess the property of
thixotropy, whereby the viscosity of the medium at a preset
temperature and a given concentration of the dispersed phase can by
changed by applying an external action. The type and degree of this
action must be sufficient to provide that the kinetic units of the
colloidal system could acquire the necessary orientation and form a
base structure for the required film. The direct action upon the
coating liquid and the formation of a wet film is performed by the
liquid film applicator (FIG. 3, 120) as it moves along the
substrate (105). Special features of the liquid film applicator
design allow this device to produce the necessary orienting action
upon the material structure and to form an even wet layer of preset
thickness with a smooth surface.
[0075] Anisotropic optical films can also be formed using inorganic
lyotropic liquid crystals, for example, based on iron oxohydroxide
or vanadium oxide, which possess anisotropic electrical and
magnetic properties.
[0076] Use of the present invention is by no means restricted to
the formation of coatings based on of liquid-crystalline and
colloidal systems with anisometric particles. Any liquid capable of
forming a coating on the given substrate can be applied using this
system as well.
[0077] The possible substrate materials are plastics, glass, and
other materials, including polymeric films. Prior to film
application, the substrate usually treated by certain means (e.g.,
corona discharge, surfactants, etc.) to render it homogeneously
hydrophilic over the entire surface. A substrate holder may be
employed, which is usually a vacuum table, which reliably ensures
that the substrate is immobile during the film application and
provides leveling of the substrate surface.
[0078] To those skilled in the art it will be understood that there
can be many other variations of the embodiments what have been
described above while still achieving the same objectives of the
invention. Such variations are intended to be covered by the scope
of this invention. As such, the foregoing description of
embodiments of the invention is not intended to be limiting.
Accordingly, it is intended that the appended claims will cover all
modifications of the invention that fall within the true spirit and
scope of the invention.
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